This invention relates to an improved pressure welding apparatus and more particularly to an improved cable welding tool.
The advantages of cold pressure welding are well known in the art. Various machines and mechanisms have been provided for accomplishing cold pressure welds, particularly for cold welding wires. Because of the fact that pressure rather than heat is used to achieve the welding upset, the tool must generate very high forces. For this reason, the cold welding tools that have been previously proposed are relatively large and heavy machines. Although there have been proposed relatively small machines, these machines have been limited to applications in which extremely fine wires were welded and even then the tools were bench operated.
Recently, a need has been found for achieving good splices in coaxial cables. The signal transmitted via coaxial cables will experience spurious reflections and/or signal deterioration if the splices change the diameter of the conductor. Furthermore, conventional cable splices that depend upon soldered connections, slip fit parts or compression fittings may pull apart and create open circuits when subjected to thermal cycling or mechanical stresses. The splicing of coaxial cables, therefore offers an excellent opportunity for the application of cold pressure welding. Cold pressure welding provides a superior electrical connection with no significant change in the wire diameter. The strength of cold pressure welds also is comparable to the strength of unspliced conductors.
Often times, these cables are carried by overhead poles. Because such splices must be made in the field and at times at the top of a utility pole, the previously proposed cold welding machines cannot be used due to their aforenoted defects as to size.
It is, therefore, a principal object of this invention to provide an improved and compact cold pressure welding tool.
It is another object of this invention to provide a hand held tool that is adapted for use in cold pressure welding of such parts as coaxial cables.
It is a further object of the invention to provide a compact cold pressure welding tool embodying an efficient force amplifier.
In connection with achieving a compact tool that is light in weight and which nevertheless incorporates a force amplification mechanism, the use of a hydraulic device for force amplification offers many advantages.
It is therefore, another object of this invention to provide a hydraulically operated cold pressure welding apparatus that has a compact construction.
Cold welding tools normally include pairs of dies that drip and upset the workpieces. These dies must be supported for movement in accurately defined paths so as to insure good pressure welds. In order to so support the dies it has been the practice to mount the dies in a rigid housing. However, cold pressure welding results in the formation of an upset or flash area around the weld joint. Frequently, this flash will become dislodged from the weld workpieces and jammed between the dies. It is, therefore, necessary to disassemble the apparatus to permit cleaning of the dies and to inspect the dies machined surfaces.
It is, therefore, still another object of this invention to provide a cold pressure welding tool in which the welding dies may be conveniently inspected, cleaned and replaced.
It is another object of the invention to provide a cold pressure welding tool having a housing made up of two pivotally supported members each of which supports a portion of the die assembly for facilitating cleaning and removal of the dies.
As has been previously noted, most cold pressure welding tools employ two pairs of dies which dies move relative to each other to both grip and upset the workpiece. It is necessary to incorporate a mechanism for moving the dies in a predetermined sequence. Furthermore, it is necessary to accurately locate the dies relative to each other.
It is yet a further object of this invention to provide an improved cold pressure welding apparatus incorporating an improved arrangement for achieving the sequencing operation of the dies.
It is still a further object of this invention to provide an improved cold pressure welding apparatus in which the die location is simplified.
In cold pressure welding, the pieces to be welded are normally gripped by welding dies which dies are moved toward and away from each other to achieve an upset of the ends of the pieces. Because the weld is generated by the application of pressure without heat, considerable forces are required to achieve the weld. It is desirable, because of the force experienced, to provide some mechanism that limited the force applied to the welded pieces and to the welding dies to prevent damage.
It is, therefore, yet another feature of this invention, to provide an improved cold pressure welding apparatus that incorporates a device for limiting the forces applied to the workpieces and to the welding dies.